Biomimetic supramolecular nanostructures based on polycaprolactone and nanosized calcium phosphate

Nanocomposites based on polycaprolactone (PCL) and calcium phosphate (CaP) have recently been proposed for applications in bone repair and regeneration.1,2 However, very limited studies have investigated the fabrication of 3D porous composites using the supramolecular PCL. Hence, in this study, ureidopyrimidinone groups (Upy) was first synthesized using 1,6-hexamethylene diisocyanate and 2-amino-4-hydroxy-6-methyl pyrimidine and then PCL with n= 2000 g/mol and CaP with spherical morphology wasfunctionalized by the as-synthesized Upy groups. Presence of UPy in the polymer structure was subsequently determined by Fourier-transform infrared (FTIR) spectroscopy according to the characteristic peaks observed at 1450 cm−1–1690 cm−1. Moreover, modification of CaP with UPy groups was again confirmed by FTIR; the NCO in UPy (2275 cm−1) completely disappeared and the peaks at 1645, 1668, and 1697 cm−1 indicated the formation of a urethane linkages. The resulting modified CaP (CaPUPy) was finally conjugated with the supramolecular polymer to fabricate a new PCLUpy2/CaPUpy nanocomposite. The results showed that mechanical properties can be significantly increased by incorporating appropriate orientation of hydrogen bonds in the supramolecular structure (Fig. 1). Accordingly, the nanocomposites reported here may provide a new opportunity to create supramolecular structures based on the reversible assemblies for the applications in bone tissue regeneration.

Keywords:

Supramolecular polycaprolactone , Ureidopyrimidinone , calcium phosphate , Quadruple hydrogen-bonding , Bone tissue